1. Field of the Invention
The present invention relates to a coordinate input device in which data are inputted by operating an operating area with an input device such as a pen.
2. Description of the Related Art
FIG. 4A is a sectional view of the main portion of a conventional coordinate input device, and FIG. 4B is a sectional view taken along the line 4B--4B of FIG. 4A.
As shown in FIGS. 4A and 4B, in the conventional coordinate input device, a transparent lower electrode 22 composed of an ITO film (a resistive film formed of indium oxide) is provided over the entire upper surface of a substrate 21 composed of transparent rectangular sheet glass, and a plural spacers 23 composed of a transparent insulating material are provided on the upper surface of the lower electrode 22, spaced at intervals.
A transparent upper electrode 25 composed of an ITO film is provided over the entire lower surface of a film 24 composed of a transparent plastic such as polyethylene terephthalate. The upper electrode 25 is opposed to the lower electrode 22 and is placed on the spacers 23. Thus, the lower electrode 22 and the upper electrode 25 are combined, being isolated from each other.
When such a coordinate input device is used, it is, for example, placed on a liquid crystal display device or the like. The information displayed on the liquid crystal display device is visually perceived by the operator through the coordinate input device. In response to this, an input device (not shown in the drawing), such as an input pen, is pressed against the film 24 to cause deformation, and the upper electrode 25 is brought into contact with or separated from the lower electrode 22, and thus a desired coordinate is inputted.
However, although the conventional coordinate input device is composed of transparent materials, since materials having different refractive indices are deposited, the light passing through the coordinate input device may be attenuated or reflected, and thus the transmittance therethrough cannot be 100%. When the coordinate input device is combined with a liquid crystal display device or the like, the displayed content may be attenuated, resulting in reduced visibility in comparison to the liquid crystal display device alone. Therefore, a method for increasing transmittance through a coordinate input device is desired.